The present invention relates to a fine particle of aluminum hydroxide for filling in a resin, which is used as a flame retardant or the like in plastic, rubber and the like, and also relates to a resin composition comprising the fine particle of aluminum hydroxide.
The aluminum hydroxide has been conventionally used over the wide range as a filler for filling in rubbers and plastics, for example, as a flame retardant in a thermoplastic resin, a rubber and an epoxy resin or as a toning filler in a thermosetting resin such as unsaturated polyester resin and acrylic resin.
In the case of using the aluminum hydroxide as a flame retardant, the flame resistance is more improved as the amount of aluminum hydroxide filled is larger. However, if the amount filled is increased, the moldability or kneading torque increases and in turn the molding temperature increases, as a result, the aluminum hydroxide disadvantageously undergoes partial dehydration and foaming. In the case of filling the aluminum hydroxide into a thermosetting resin, the material cost may be lowered by increasing the amount filled, however, a problem arises, such as deterioration in the mold-workability or reduction in the curing speed.
A resin composition obtained by filling fine particles of aluminum hydroxide in an unsaturated polyester resin, acrylic resin or the like is especially used as an artificial marble for the constructive material of bath tab, kitchen counter and the like. However, in order to bring out a texture (solemnity) close to natural marble, a large amount of fine particles of aluminum hydroxide must be filled into the resin.
For solving these problems, various techniques have been heretofore disclosed, for example, (1) a method of using a mixture with agglomerated coarse particles as a primary particle or fine particles obtained by grinding the coarse particles (see, JP-B-5-48782 (the term xe2x80x9cJP-Bxe2x80x9d as used herein means an xe2x80x9cexamined Japanese patent publication)) and (2) a method of grinding a particulate aluminum hydroxide specified in the particle diameter or soda content to obtain aluminum hydroxide having a small specific surface area (see, JP-B-4-6648 and JP-B-6-49573) are known.
The technique (1) above has a problem in that coarse particles used alone precipitate at the molding and this causes reduction in the surface smoothness or in the strength of the molded article and when used in combination with fine particles, the curing time is prolonged as the specific surface area is increased. In the technique (2), the curing time is also prolonged due to increase in the specific surface area after the grinding or cracking of agglomerated particles and when these particles are used alone, the amount filled is limited because the particles are fine.
In order to improve the filling property into a resin, a surface treatment with a fatty acid, a silane coupling agent or the like is often performed.
Under these circumstances, the object of the present invention is to improve conventional fine particles of aluminum hydroxide for filling in a resin such as plastic and rubber and provide a fine particle of aluminum hydroxide which can be reduced in the viscosity at the filling into a resin to attain high filling and when filled into a thermosetting resin, can ensure reduction in the curing time and more increase in the productivity. The object of the present invention includes providing a resin composition comprising the fine particle of alumina hydroxide.
As a result of extensive investigations to develop an aluminum hydroxide having the above-described preferred properties, the present inventors have found that when a fine particle of aluminum hydroxide is obtained by blending at least two components (binary system), preferably three components (ternary system), the object of the present invention can be attained. The present invention has been accomplished based on this finding. More specifically, the present invention provides the following inventions.
[1] A fine particle of aluminum hydroxide for filling in a resin, which has properties such that when 200 parts by weight of the fine particle of aluminum hydroxide is filled into 100 parts by weight of an unsaturated polyester resin (Rigolac 2004WM-2, produced by Showa Highpolymer Co., Ltd.), the viscosity can be less than 200 poises in the measurement at 35xc2x0 C. by a Brookfield viscometer and that when 150 parts by weight of the fine particle of aluminum hydroxide is filled into a resin composition comprising 100 parts by weight of another unsaturated polyester resin (Polylite TP-123, produced by Dai-Nippon Ink and Chemicals, Inc.) and 2 parts by weight of methyl ethyl ketone peroxide, the curing time until the viscosity becomes immeasurable due to the curing of resin can be less than 20 minutes in the measurement at 35xc2x0 C. by a Brookfield viscometer.
[2] A fine particle of aluminum hydroxide comprising a particulate aluminum hydroxide X having a BET specific surface area of 1.0 m2/g or less and a secondary particle size of 35 to 150 xcexcm, a particulate aluminum hydroxide Y having a BET specific surface area of 1.0 m2/g or less and a secondary particle size of 10 to 35 xcexcm, and a particulate aluminum hydroxide Z having a BET specific area of 3.0 m2/g or less and a secondary particle size of 0.5 to 10 xcexcm, in a compositional mass ratio falling in the area surrounded by four points of Point xcex1 (X:Y:Z=47.5:25.0:27.5), Point xcex2 (X:Y:Z=47.5:50.0:2.5), Point xcex3 (X:Y:Z=82.5:0.0:17.5) and Point xcex4 (X:Y:Z=72.5:0.0:27.5) including the lines in the ternary composition diagram shown in FIG. 1 where the entire is assumed to be 100% by mass.
[3] A fine particle of aluminum hydroxide comprising a particulate aluminum hydroxide X having a BET specific surface area of 1.0 m2/g or less and a secondary particle size of 35 to 150 xcexcm, a particulate aluminum hydroxide Y having a BET specific surface area of 1.0 m2/g or less and a secondary particle size of 10 to 35 xcexcm, and a particulate aluminum hydroxide Z having a BET specific area of 3.0 m2/g or less and a secondary particle size of 0.5 to 10 xcexcm, in a compositional mass ratio falling in the area surrounded by four points of Point A (X:Y:Z=50.0:25.0:25.0), Point B (X:Y:Z=50.0:45.0:5.0), Point C (X:Y:Z=80.0:0.0:20.0) and Point D (X:Y:Z=75.0:0.0:25.0) including the lines in the ternary composition diagram shown in FIG. 2 where the entire is assumed to be 100% by mass.
[4] The fine particle of aluminum hydroxide as described in [2] or [3], wherein the particulate aluminum hydroxide X has a secondary particle size of 50 to 150 xcexcm, the particulate aluminum hydroxide Y has a secondary particle size of 10 to 25 xcexcm and the particulate aluminum hydroxide Z has a secondary particle size of 0.5 to 8 xcexcm.
[5] A resin composition comprising the fine particle of aluminum hydroxide described in any one of [1] to [4].
[6] A resin composition comprising the fine particle of aluminum hydroxide described in any one of [1] to [4], wherein the viscosity measured at 35xc2x0 C. by a Brookfield type viscometer is less than 200 poises.
[7] A resin composition comprising the fine particle of aluminum hydroxide described in any one of [1] to [4], which is a resin composition for forming an artificial marble.
[8] A resin composition comprising the fine particle of aluminum hydroxide described in any one of [1] to [4], which comprises at least one resin selected from the group consisting of an unsaturated polyester resin, an acrylic resin, a vinyl ester resin and an epoxy resin.
[9] A resin composition comprising the fine particle of aluminum hydroxide described in any one of [1] to [4], which is a cured resin composition.